Avoid "DLL download" sites. If the download is under 50KB, it is likely a fake. A real simg2img.exe is usually between 50KB and 200KB.
You downloaded system.img from a Samsung firmware and want to mount it. Simg2img.exe Download
This article provides everything you need to know about the , its installation, and how to use it to convert Android sparse images into raw, mountable images. What is Simg2img.exe? Avoid "DLL download" sites
If an OTA update fails, you can extract the payload.bin , locate the sparse partition images, convert them with simg2img , and manually recover user data. you can extract the payload.bin
img2img.exe sparse_image.img raw_output.img